This article was originally published in the March/April 1995 issue of Home Energy Magazine. Some formatting inconsistencies may be evident in older archive content.

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Home Energy Magazine Online March/April 1995

trendsin energy

PRISM Does Windows

A new and improved version of the most widely used computer software for analyzing retrofit energy savings from utility billing data is now available. It's a completely new version that combines many statistical enhancements in a Windows-based user interface, said Margaret Fels, who first developed PRISM in 1982 at Princeton University's Center for Energy and Environmental Studies for use in its Modular Retrofit Experiment.

The new version (Advanced Version 1.0) requires an IBM-compatible personal computer and Microsoft Windows 3.1 or 3.11. The previous program, PRISM Version 4.0, has been used by more than 300 organizations worldwide, including utilities, energy consultants, energy service companies, universities, researchers, energy auditors, and government agencies.

PRISM is an acronym for PRInceton Scorekeeping Method. PRISM calculates a weather-corrected index of energy consumption from which energy savings (and their accuracy) may be computed (see PRISM: a Tool for Tracking Retrofit Savings, HE Nov/Dec '87 p. 27, and Now That I've Run PRISM, What Do I Do With the Results? HE Sep/Oct '90 p.27). To run PRISM, the user must assemble and enter average daily outdoor temperature data (obtained from a nearby weather station) and the whole-house utility consumption data (generally obtained from monthly utility bills) for at least one year before and one year after an energy conservation retrofit. The program then estimates the energy use of the building adjusted for the severity of the winter and/or summer, called the Normalized Annual Consumption.

All current PRISM users should replace their Version 4.0 with the Advanced Version 1.0, Fels said. It's a very different program that will provide much better numbers through data correction features that will yield more complete and more reliable results, she said. In addition the entire billing analysis process, from data entry to final savings summaries, is greatly enhanced.

New features include:

Heating-and-Cooling (HC) PRISM model, in addition to the Cooling-Only (CO) model and the Heating-Only (HO) model available in the original version

Robust enhancements for HO and CO

Automated model selection

Automated correction of estimated readings

Identification of outliers in the consumption data

Interactive consumption plots

Data input translators for consumption and temperature data

Summaries of savings results for participant and control groups in graphical and statistical summary form

Fels also noted that the new version may be run on aggregate utility sales, as well as with individual building data, and that it enables incorporation of reliability criteria.

PRISM (Advanced Version 1.0) is available to all members of the Electric Power Research Institute (EPRI) through the EPRI Software Center. Others can order copies from the Center for Energy and Environmental Studies, Engineering Quadrangle, Princeton University, Princeton, NJ 08544. Tel:(609)258-5445. (Contact: Michelle Marean or Kelly Kissock). Cost of the program is $795 for utilities, government agencies, and energy consulting and energy service companies. The price for colleges and universities (and for additional site licenses) is $395.